Insights on film growth conditions on a floating substrate during reactive Ar/O₂ bipolar High Power Impulse magnetron sputter deposition.

Abstract
We report several effects found in reactive bipolar high-power impulse magnetron sputtering (bipolar HiPIMS or BPH) discharges at the substrate level. The role of the negative peak current and the positive pulse voltage, U+, on the deposition flux at the electrically insulating substrate is discussed and the results are compared to conventional DC discharges. In particular, the normalized energy flux, Φn, delivered to the substrate is higher under BPH conditions at U+=+300 V (Φn=3.43x1015 eV.nm−3) as compared to the HiPIMS (Φn=0.78x1015 eV.nm−3) and DCMS (Φn=1.23x1015 eV.nm−3) regimes which is assumed to be provoked by an intensification of the positive ion bombardment. Accordingly, the mean energy and count of positively charged metal and gaseous ions increase in line with U+ as measured by energy-resolved mass spectrometry. Contrariwise, our analysis has shown a significant decrease (∽20 %) of negative oxygen ion count under BPH conditions.